Lighting units or lighting assemblies using semiconductor light sources such as light-emitting diode (LED) chips are becoming more popular as advances in technology have led to economic and yet very bright semiconductor light sources.
In lighting assemblies used in automotive applications, for example, a particular requirement is that the bright/dark cut-off line of the light output by the lighting assembly satisfies certain regulations. Furthermore, this bright/dark cut-off line should be adaptable, for example to raise or lower the beam of light output by the lighting assembly so that a low beam and a high beam can be produced. Adaptability of the light output is also desirable in certain situations, such as when driving into a bend, so that the area in the bend can be better illuminated, with a resulting increase in safety. Furthermore, it may be advantageous to influence the amount of light in the foreground of beam pattern, i.e. in a region of the beam closest to the vehicle, depending on traffic conditions and/or terrain, weather conditions, etc.
Prior art lighting assemblies that implement a movable beam limiter to direct the light output to alter the bright/dark cut-off line, for example in an up or down direction, are known, for example WO 2008/035267 A2, which describes a moveable beam-limiter with a side wall that can be bent to a curved surface. This realization makes use of a collimating reflector together with an additional beam-limiter to alter the shape of the resulting light beam. However, these solutions generally also require additional parts to prevent the light ‘escaping’ through gaps arising when the beam limiter is moved. The light escaping at the edges results in a beam with diffuse edges, which is undesirable. Furthermore, since not all of the light emitted by the light source passes through the beam limiter, these prior art systems are characterized by a lower efficiency. Also, beam limiter solutions which attempt to solve the problem of the escaping light are rather complex, and are therefore costly to manufacture.
Therefore, it is an object of the invention to provide an alternative, more efficient and more economical lighting assembly.